docs: def pre_process_code_block(block):
          """Preprocess the content of a code block, modifying the code
          block in place.
  
          Just dedents indented code.
          """
          if 'indent' in block and block['indent']:
              indent = r'^' + block['indent']
              block['content'] = re.sub(indent, '', block['icontent'],
                                        flags=re.MULTILINE)